Method for marking a textile thread with a fluorescent element, textile thread produced by the marking method, and use of said textile thread for weaving an item of clothing

ABSTRACT

A method for marking a textile thread by a fluorescent element has the following successive steps: placing a textile thread and at least one fluorescent element in a reaction chamber, introducing a fluid into the reaction chamber, increasing the temperature and pressure in the reaction chamber up to a temperature and a pressure so as to transform the fluid into a supercritical fluid and to mark the textile thread by the fluorescent element. The fluorescent element is chosen from organolanthanide complexes.

BACKGROUND OF THE INVENTION

The invention relates to a method for marking a textile thread by afluorescent element and also relates to a textile thread obtained bysaid method.

STATE OF THE ART

An increasing number of manufactured products are the object offraudulent reproduction. The counterfeited products are difficult todistinguish from the original products, in particular due to the qualityof the reproduction and/or on account of the fact that they can bedistributed through the same distribution channels as the originalproducts.

The textile sector is one of those that is most affected by thesereproductions.

In addition to the economic losses (loss of jobs, loss of turnover forthe companies), the reproductions are often manufactured underunsuitable hygiene conditions and by under-qualified manpower, whichmakes these products dangerous for health not only for the employees butalso for consumers.

It is essential to set up actions aiming to protect these products,often copied practically identically.

To facilitate detection of copies, certain products can be marked withan authenticating element. This can involve a secured optic markingsuitable for textile labels.

OBJECT OF THE INVENTION

The object of the invention is to remedy the shortcomings of the priorart, and in particular to propose a method for marking an item ofclothing that is simple and easy to implement, the marking having to bedifficult to copy and at the same time easily identifiable.

This object tends to be achieved by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from thefollowing description of particular embodiments of the invention givenfor non-restrictive example purposes only and represented in theappended drawings, in which:

FIG. 1 represents a photograph of a textile thread, marked according tothe method of the invention, and of an unmarked textile thread,

FIG. 2 represents a photograph of the two textile threads of FIG. 1,illuminated under an ultraviolet lamp,

FIG. 3 represents an emission spectrum of a textile thread markedaccording to the method of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The method for marking a textile thread by a fluorescent elementcomprises the following successive steps:

-   -   placing a textile thread and at least one fluorescent element in        a reaction chamber,    -   introducing a fluid into the reaction chamber,    -   increasing the temperature and pressure in the reaction chamber        up to a temperature Ts, higher than the critical temperature of        the fluid Tc, and up to a pressure Ps, higher than the critical        pressure of the fluid Pc, so as to transform the fluid into a        supercritical fluid and to mark the textile thread by the        fluorescent element.

In the textile field, supercritical fluids, such as carbon dioxide, canbe used for colouring/impregnating textile materials such as syntheticfibres of polyester type with pigments (document EP 1,126,072 and Kikicand al., Current Opinion in Solid State and Materials Science 2003, 7,399-405). The method enables the quantity of waste/polluted water to besignificantly reduced compared with conventional dyeing methods.

The method does however require the use of a small quantity of water, inthe reaction chamber, for example in the form of a relative humiditycomprised between 10% and 100%, to improve the reactivity and/oraccessibility of the fibres.

However, such a marking, that is only visual, is fairly easy tocounterfeit.

The method for marking is a method for marking a textile thread by afluorescent element. A distinctive fluorescent element is placed on thetextile thread. The marking is a fluorescent marking.

The marking is advantageously invisible to the naked eye and thereforedifficult to identify by a person not knowing the specificity of themarking.

What is meant by method for marking is a method which enables thematerial to be marked without impairing its properties, and inparticular without colouring it.

The marking is advantageously homogeneous. The marking can be made onthe surface or in the volume of the material.

Marking in the volume of the material advantageously enables markingboth at the surface and in depth. Even if the molecules at the surfacelose their properties or are eliminated on account of the successivewashings and/or long exposure to the sun, the in-depth molecules can actas a reservoir. The lifetime of the material is thus increased.

After marking, the fluorescent element is linked to the textile thread.The fluorescent element cannot be dissociated from the textile thread bysimple washing for example. The resistance of the marking also resistsethanol, acetone and water. The marking can also no longer be removed bysimple rubbing of a cloth on the textile thread obtained.

What is meant by textile thread is an agglutination of textile fibres toform a long assembly. The textile threads are designed to be woven inorder to form fabrics for confection of items of clothing for example.

The textile thread is a synthetic textile thread made from polymer, orfrom cotton or leather.

The synthetic textile thread comprises 1% to 88.5% by weight of apolymer material.

Preferentially, the polymer material is polyester: the textile threadcomprises 1 to 88.5% by weight of polyester.

The polyester can be chosen from polyglycolic acid (PGA), polylacticacid (PLA), polycaprolactone (PCL), polyhydroxyalcanoate (PHA),polyethylene adipate (PEA), polybutylene succinate (PBS), polyethyleneterephtalate (PET), polybutylene terephtalate (PBT), polytrimethyleneterephtalate (PTT), or polyethylene naphtalate (PEN).

According to a preferred embodiment, the polyester is polyethyleneterephtalate (PET).

The rest of the percentage of weight can correspond to impurities,fixing agents, colorants, etc.

For example, for a textile thread comprising 88.5% by weight of polymermaterial, the rest of the percentage can correspond to 2.3% ofimpurities, 0.7% of pre-treatment agents (to perform whitening forexample), 6.5% of colorants and colorant fixing agents, and 2% offinalisation agents (fire protection treatment, waterproofing treatment,etc.).

What is meant by fluorescent element is an element having the propertyof being able to absorb light and to re-emit it at a higher wavelength.The fluorescent element is formed by at least one fluorescent molecule.Advantageously, the fluorescent element is composed of a multitude offluorescent molecules of the same nature or of different natures.

Preferentially, the fluorescent molecules are of the same nature.

The quantity of fluorescent molecules is chosen in such a way as to besufficient to be able to impregnate the textile thread and to give itdetectable fluorescent properties.

The fluorescent element is preferably chosen from phthalocyanines andorganolanthanide complexes.

According to a preferred embodiment, the fluorescent element is anorganolanthanide complex. Advantageously, the use of an organolanthanidecomplex enables the material to be marked not to be coloured. Themarking is invisible to the naked eye.

Organolanthanide complexes, also called lanthanide complexes, are formedfrom trivalent lanthanide ions, noted Ln³⁺, and from organic molecules,called ligands. The ligands are for example β-diketonates or carboxylicacids.

Advantageously, emission of the lanthanide complexes is characterised byvery thin strips positioned at well-defined wavelengths: each lanthanidecomplex has its own optic footprint.

It is therefore possible to specifically mark a textile thread with aparticular wavelength.

Organolanthanide complexes formed from Ce³⁺ and Gd³⁺ ions emit in thenear-UV spectral ranges and enable the textile thread to be marked by afluorescent element in the near-UV; the complexes formed from Tm³⁺ ionsin the blue; the complexes formed from Tb³⁺ and Er³⁺ ions in the green;the complexes formed from Dy³⁺ ions in the yellow; the complexes formedfrom Sm³⁺ ions in the orange; the complexes formed from Er³⁺ and Eu³⁺ions in the red, and the complexes formed from Nd³⁺, Er³⁺, Tm³⁺, andYb³⁺ ions in the near infrared.

It is possible to associate several lanthanide complexes to obtain morecomplex optic signatures.

Advantageously, the lanthanide complexes are dispersed in homogeneousmanner in the textile thread and are invisible to the naked eye. Themarking does not modify the appearance of the product. The marking issaid to be furtive.

Subjected to a suitable luminous excitation, their fluorescence isdetectable by any suitable device. This device can for example be aportable spectrometer. The presence of lanthanide complexes can inparticular be detected with inexpensive detectors available on themarket.

Preferentially, the organolanthanide complex is a europium complex.

According to another embodiment, the fluorescent element is aphthalocyanine. The use of phthalocyanine makes it possible to obtainboth a fluorescent marking and colouring of the thread. The thread canadvantageously be used to make a particular pattern, visible to thenaked eye, when weaving of the item of clothing is performed.

The phthalocyanine can be a phthalocyanine or a phthalocyaninederivative. In particular, it can be1,4,8,11,15,18,22,25-Octabutoxy-29H,31H-phthalocyanine,5,9,14,18,23,27,32,36-Octabutoxy-2,3-naphthalocyanine,5,9,14,18,23,27,32,36-octabutoxy-2,3-copper naphthalocyanine (II), or1,4,8,11,15,18,22,25-octabutoxy-29H,31H-nickel phthalocyanine (II).

The fluorescent element is advantageously inserted in the reactionchamber in the form of a powder.

The fluorescent element can be mixed with the fluid or placed beside itin the reaction chamber.

The substrate can be immersed in the fluid at the beginning of themethod, or it can be placed beside it.

The fluid is transformed into a supercritical fluid when it is heated toa temperature Ts higher than its critical temperature T_(c) and when itis compressed at a pressure Ps higher than its critical pressure P_(c).

To obtain the supercritical fluid from the fluid, the chamber istherefore heated so as to reach a pressure Ps higher than pressure P_(c)and a temperature Ts higher than pressure T_(c).

The supercritical fluid generally presents a volumetric mass densityclose to that of the liquid and a viscosity close to that of the gas.The supercritical fluid enables a better diffusion than thecorresponding liquid phase. It also enables surface tensions to bereduced.

Preferentially, the fluid is inserted in the chamber in liquid form.According to an alternative it could be inserted in gaseous form.

Otherwise, the fluid could be inserted in the reaction chamber insupercritical state.

The supercritical fluid is advantageously inert with respect to thetextile thread.

Preferentially, the fluid inserted into the reaction chamber is carbondioxide. Even more preferentially it is liquid carbon dioxide.

This is a solvent referred to as “environment-friendly solvent”, i.e. itis non-polluting for the environment. The method involving the use ofcarbon dioxide does not generate aqueous or organic polluting rejects,which are harmful for the environment.

Preferentially, pressure Ps and temperature Ts are maintained for aduration of at least 15 minutes. This duration enables a homogeneous andcontinuous coating to be achieved, at least at the surface of thetextile thread.

Advantageously, the duration is comprised between 15 minutes and 10hours. The choice of the duration enables the quantity of fluorescentmolecules penetrating into and being fixed in the textile thread to bedefined.

Preferentially, pressure Ps is comprised between 100 bars and 400 bars,and even more preferentially between 300 bars and 350 bars.

Preferentially, temperature Ts is comprised between 50° C. and 200° C.,and even more preferentially temperature Ts is comprised between 110° C.and 150° C.

These pressure and temperature ranges make it possible to be positionedbeyond the critical point of the fluid and to transform the carbondioxide into supercritical carbon dioxide. Pressure Pc and temperatureTc of the critical point are, for carbon dioxide, respectively 31° C.and 74 bars.

The supercritical fluid is then absorbed by the textile thread: thesupercritical fluid penetrates into the fibres of the textile thread.The fluorescent element is drawn into the textile thread by thesupercritical fluid.

The supercritical fluid enables the fluorescent element to be trapped inthe textile thread: the textile thread is impregnated, marked by thefluorescent element.

Once the textile thread has been impregnated, the pressure and/ortemperature are dropped back below the critical fluid point so as toeliminate the fluid absorbed by the textile thread. The pressure andtemperature are then reduced until an ambient temperature and pressureare reached.

A textile thread marked by a fluorescent element is obtained. Thefluorescent molecules are trapped in the textile thread under ambienttemperature and pressure conditions (i.e. around 20-25° C. and 1 bar).

According to a particular embodiment, a solvent is placed in thereaction chamber. Advantageously, the solvent is placed in the reactionchamber before the supercritical fluid is inserted.

The solvent enables the fluorescent element be more easily solubilised.A larger quantity of fluorescent element can be used, whichadvantageously enables the reaction time necessary for obtaining markingof the textile thread to be limited.

The solvent is preferably an organic solvent. The fluorescent elementadvantageously presents a better solubility in an organic solvent.

The solvent is advantageously chosen from dichloromethane, ethanol,acetone, tetrahydrofurane and trichloromethane.

The method requires little or no solvents, depending on the embodiments.There are therefore less fluorescent elements lost in the solventcircuit. The effluents do not need to be treated. This point isparticularly advantageous as one of the main problems of industriesspecialised in textiles is processing of residues (Directive 2008/1/EC).

In one embodiment, the method does not require the use of water. Thefluid does not contain any water and the solvent does not contain anywater.

The method will be described by means of the following examples givenfor non-illustrative and non-restrictive example purposes only.

For each of the following examples, a textile thread is placed in atubular reaction chamber equipped with a pressure gauge and athermometer. The marker, i.e. the fluorescent element, is also insertedin the reaction chamber.

The weight ratio between the textile thread and fluorescent element iscomprised between 1% by weight and 20% by weight. Preferentially theweight ratio between the textile thread and fluorescent element is10%±1%.

At this stage of the method, an organic solvent can also be inserted. Itcan be inserted by means of a graduated syringe.

The solvent volume is comprised between 0.5 mL and 1 mL.

The reactor is then loaded with liquid CO₂ until a first pressure of 80bars±20 bars is obtained, i.e. 60 bars to 100 bars.

The reactor is then heated by means of heating element up to atemperature Ts comprised between 50° C. and 200° C. The temperature ischosen according to the required pressure Ps, pressure Ps beingcomprised between 100 bars and 400 bars.

The CO₂ is then in its supercritical state, i.e. at a higher temperaturethan the temperature of the critical point Tc of 31° C. and at a higherpressure than the pressure of the critical point Pc of 74 bars, whichenables transfer of the fluorescent molecule at the surface and/or inthe volume of the textile thread.

The conditions are kept constant during a time t comprised between 15minutes and 10 h.

After the heating has been stopped, the temperature of the reactionchamber will be progressively reduced to ambient temperature, and theresidual pressure is then broken, the pressure being stabilised atambient pressure, i.e. around 1 bar.

The table below sets out different tests performed.

no Ts (° C.) Ps (bar) Time (h) Element PET weight (mg) 1 130 300 0.5 Eucomplex 500 2 150 300 2 Eu complex 190 3 110 350 8 Phthalocyanine 300

The phthalocyanine of example no 3 is1,4,8,11,15,18,22,25-Octabutoxy-29H,31H-phthalocyanine.

Marking of the polymer substrates by the fluorescent element wasobserved with the naked eye, under an ultraviolet (UV) lamp and byconfocal optical microscopy.

FIG. 2 represents a textile thread marked by a europium complex and anunmarked textile thread under daylight and FIG. 3 represents the sametextile thread under ultra-violet lighting (UV at 365 nm).

Under ultra-violet lighting, the marked thread is red. The fluorescencein the red is clearly visible. The control sample is not fluorescent.

The emission spectrum of the thread marked by the europium complex wasmeasured with an Ocean Optics portable spectrometer—FIG. 3.

The method enables a textile thread marked by at least one fluorescentelement to be obtained.

The fluorescent element is preferentially chosen from phtalocyanines andorganolanthanide complexes.

The fluorescent element is advantageously a europium complex.

The textile thread can be marked by several fluorescent elements.

The textile thread comprises between 1% and 88.5% by weight ofpolyester.

The textile thread is used to weave at least a part of an item ofclothing.

The item of clothing comprises at least one textile thread obtainedaccording to the method described in the foregoing.

Advantageously, the marking is incorporated in the item of clothing: itis incorporated in the product and is therefore resistant to tearingand/or to friction, unlike markings made on clothing labels.

This type of marking is also resistant to washing and rinsing. Thefluorescent marking enables an authentication throughout the life cycleof the product.

One or more markings can be included in the same item of clothing,thereby enhancing protection of the products.

This type of marking, due to these specificities, is highly secured andparticularly difficult to copy. Detection of the marking is easy and itis therefore easy to detect imitations.

1-17. (canceled)
 18. Method for marking a textile thread by afluorescent element comprising the following successive steps: placing atextile thread and at least one fluorescent element in a reactionchamber, introducing a fluid into the reaction chamber, increasing thetemperature and pressure in the reaction chamber up to a temperature,higher than the critical temperature of the fluid, and up to a pressure,higher than the critical pressure of the fluid, so as to transform thefluid into a supercritical fluid and to mark the textile thread by thefluorescent element, wherein the fluorescent element is chosen fromorganolanthanide complexes.
 19. Method according to claim 18, whereinthe supercritical fluid introduced into the reaction chamber is liquidcarbon dioxide.
 20. Method according to claim 18, wherein the textilethread comprises from 1% to 88.5% by weight of polyester.
 21. Methodaccording to claim 20, wherein the polyester is ethylenepolyterephtalate.
 22. Method according to claim 18, wherein thefluorescent element is a europium complex.
 23. Method according to claim18, wherein the weight ratio between the textile thread and thefluorescent element is comprised between 1% and 20% by weight. 24.Method according to claim 18, wherein the pressure and temperature aremaintained during a period of at least 15 minutes.
 25. Method accordingto claim 24, wherein the pressure and temperature are maintained duringa period comprised between 15 minutes and 10 hours.
 26. Method accordingto claim 18, wherein the pressure is comprised between 100 bars and 400bars.
 27. Method according to claim 26, wherein the pressure iscomprised between 300 bars and 350 bars.
 28. Method according to claim18, wherein the temperature is comprised between 50° C. and 200° C. 29.Method according to claim 28, wherein the temperature is comprisedbetween 110° C. and 150° C.
 30. Method according to claim 18, wherein asolvent is placed in the reaction chamber before the fluid isintroduced.
 31. Method according to claim 18, wherein severalfluorescent elements are arranged in the reaction chamber.
 32. Textilethread, obtained by means of the method according to claim 18, saidtextile thread being marked by at least one fluorescent element chosenfrom organolanthanide complexes.
 33. Textile thread according to claim32, wherein the thread comprises between 1% and 88.5% by weight ofpolyester.
 34. Textile thread according to claim 32, wherein thefluorescent element is a europium complex.
 35. Textile thread accordingto claim 32, wherein the textile thread is marked by several fluorescentelements.
 36. A method comprising: weaving at least part of an item ofclothing with a textile thread according to claim
 32. 37. Item ofclothing comprising at least one textile thread according to claim 32.